Thomas Kraft of Norpac Fisheries Export inspects a database at a port facility in Indonesia. Kraft established one of the fishing industry’s first bar-code systems that give each fish a tag that can track their origins.(Photo: Firdia Lisnawati/AP)

BANGKOK - Fishing boats used high-tech systems to find vast schools of fish for decades, depleting stocks of some species and leading to the complete collapse of others.

Now, more than a dozen apps, devices and monitoring systems aimed at tracking unscrupulous vessels and the seafood they catch are being rolled out — high-tech solutions some say could also help prevent labor abuse at sea.

Illegal fishing, which includes catching undersized fish, exceeding quotas and casting nets in protected areas, leads to an estimated $23 billion in annual losses, according to the United Nations. Slavery has been documented in the fishing sectors of more than 50 countries, according to U.S. State Department reports.

“Technology is all about knowing where the fishing boats are on the ocean, but that does precious little for crews being physically abused and worked to the bone on those vessels,” he said.

Here are some emerging tech solutions:

•App for workers.

Nonprofit anti-trafficking organization Project Issara is tapping into near-ubiquitous smartphones with an app that allows Burmese and Cambodian migrant workers around the world to share information about their working conditions.

•Bar codes.

A worker runs a gadget over a fish just after it’s pulled from the boat, giving it a bar code that creates a permanent record of where it was caught. Thomas Kraft at Norpac Fisheries Export established one of the industry’s first bar-code systems that give each fish a tag that can provide details about location, boat, species and weight.

•Eyes on the Seas.

Eyes on the Seas uses satellite trackers, radar signals, drone images, even radio signals, to create a dynamic world map. Analysts using algorithms and observations can identify boats that appear to be illegally fishing in protected areas or pulling near each other to offload illicitly caught seafood.

•Global Fishing Watch.

Like Eyes on the Seas, this tool provides a nearly-live view of fishing boats at sea around the world. But the data it uses to identify boats comes almost exclusively from Automatic Identification Systems, satellite trackers used in large vessels that are easily switched on and off.

•Tech for tuna.

Cameras are recording everything that comes over the rail and onto the deck of a few dozen tuna boats loaded with motion sensors and GPS systems in the western Pacific Ocean. The goal of The Nature Conservancy’s project is to get the recording systems on thousands of tuna boats in the Palau longline fleet.